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INFLUENCE OF HYPERTENSION, HYPERGLYCEMIA, AND OBESITY ON METABOLIC SYNDROME RELATED IMPAIRMENTS IN CARDIOVAGAL BAROREFLEX SENSITIVITY

Abstract

BACKGROUND: The multi-dimensional characteristics of metabolic syndrome (MetS) pose a challenge in understanding how its individual components contribute to the impairment of cardiovagal baroreflex sensitivity (cBRS). Thus, the present study explores the hypothesis that cBRS remains significantly attenuated in individuals with MetS, even after considering the influence of resting systolic blood pressure (SBP), fasting blood glucose (FBG), and waist circumference (WC).METHODS: Both phases of the study were completed by seventy-five participants, twenty of whom met the National Cholesterol Education Panel Adult Treatment Panel III criteria for MetS, supplemented with HbA1C as a secondary indicator of glycemic control. These criteria include 1) a WC >102 cm for males and >88 cm for females (>80 cm for Asian females), 2) a SBP >130 mmHg or a diastolic (DBP) >85 mmHg, 3) a FBG >100 mg/dL or HbA1C >5.7 %, 4) a fasting triglyceride (TRG) >150 mg/dL, or 5) a high-density lipoprotein cholesterol (HDL-C) <40 mg/dL for males or <50 mg/dL for females, which were recorded in visit one. Of these 20 participants, 19 could be matched to a control participant by age, biological sex, race, and ethnicity. In the second visit, cBRS data was evaluated during ten minutes of supine rest, where heart rate, beat-by-beat blood pressure, and breathing frequency were recorded continuously and analyzed using the sequence method (systolic blood pressure change >1.0mmHg, pulse interval change >5.0ms, r>0.80, sequence length >3 beats). RESULTS: cBRSall (p<0.01), cBRSup (p<0.01), and cBRSdown (p<0.01) were shown to be significantly lower in the MetS group relative to the control. When comparisons were independently adjusted for SBP (p=0.03), FBG (p<0.01), and WC (p<0.03), cBRSall and cBRSdown remained significantly lower in the MetS group. cBRSup was also significantly depressed in the MetS group after independently adjusting for FBG (p=0.01), however, this effect was not consistent when adjusting for SBP or WC (all p>0.05). CONCLUSION: The findings of this study demonstrate cBRS remains significant impaired in MetS, independently of these three individual components, which suggests baroreflex dysfunction is an inherent characteristic of MetS.

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